In security systems, it is common to have a number of electric fence energisers operating on different conductive lines which combine to form a perimeter fence. One reason for having a number of energisers rather than just a single energiser is to enable sectorisation. For example, at a particular time one section of the security fence may be live, whereas another section of security fence may for various reasons not be live. A typical reason is that staff may be working in that area. At other times the whole of the fenced area may be live.
Another reason for having a number of energisers is in situations where the total size of the fence is greater than that which a single energiser could adequately power along.
Over the years, safety regulations have been enacted which limit the frequency and magnitude of energy pulses that can be delivered by electric fence energisers. This is to ensure that if a person or animal touches or falls against a fence and for whatever reason remains there, the electrical energy received by that person or animal is unlikely to permanently damage them.
With security systems that have two or more energisers on a security system, a problem can occur whereby at a junction between the conductive lines a person can receive a pulse having a greater magnitude than generated singly by an energiser. That is, with two energisers firing (on average every second) at a junction to both conductive lines can either receive effectively a single double every pulse resulting from the synchronous firing of the energisers, or more likely pulses at a rate less than the recommended one second apart.
The pulses received at a junction point from multiple energies shall now be referred to as an effective pulse.
These are understandably undesirable situations for safety reasons but an inevitable result of using multiple energisers for sectorisation purposes.
One possible solution to this problem is to reduce the energy output of the electric fence energisers. However, this is not an effective solution and at points of the electric fence line subject to the effects of only one energiser firing, the pulse is unlikely to be strong enough to form an effective deterrent and thus defeat the purpose of having a security system.
Another possible solution is to build physical barriers at the junction such that a person is prevented from touching conductors in a manner that would allow them to receive a compound shock. However this creates a point on the perimeter that an intruder may find much easier to cross, and would therefore defeat the purpose of having such a security system. The construction of such barriers also significantly increases the cost of the system.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.